A collapsible, height-adjustable support device with inflatable floats for mounting articles, particularly cinematographic apparatus, upon and below the water. It is characterized by a central tubular frame (1) with a plurality of detachable support arms (2) perpendicular to the central frame. The support arms also attach to the elongate inflatable buoys (10). Cinematographic apparatus is mounted upon a fixing plate (5) positioned centrally on the central frame member (1). The adjustable height of the mount above and below the surface of the water is facilitated by the angular relationship of the central longitudinally splined frame member (1) and each support arms splined hub. Footpads (4) with releasable locking pins and receiving plates (22) provide attachment of support arms to the floats (10). Anchorage and tether points (14) permit towing and static deployment.